Pavement Construction Effects on Subgrade Resilient Modulus and Validation by 3D-FE Simulation

This study investigates the changes shown by the in situ resilient modulus of compacted subgrade resulting from the construction of lime treated subgrade, base, and asphalt pavement layers. In situ modulus values are backcalculated from traditional static linear elastic layered analysis of peak deflection data of falling weight deflectometer nondestructive impact tests. Sensors 2 through 6 are more appropriate for analysis of the deflection data collected on compacted subgrade surfaces because of abnormally high sensor 1 deflections, which are above the sensor accuracy range. The data from a dynamic cone penetrometer, a destructive test, are related to layering in the subgrade soil and the modulus of each soil layer. The modulus results from both field tests agree reasonably well with the average laboratory resilient modulus values of the bottom subgrade layer for 12 selected pavement construction sites in Mississippi. Effects from the construction of top pavement layers on the subgrade modulus values are evaluated using side-by-side testing by field methods conducted over the summer, winter, spring, and following summer season. The subgrade modulus values backcalculated from the deflection tests conducted on the top constructed asphalt layer is 176% higher than the modulus for the compacted subgrade only. The nonlinear subgrade modulus calculated after full pavement construction is within 6% of the average laboratory modulus, which validates the nonlinear correction procedure of shear strain based equivalent linear analysis. The asphalt paved section is simulated by three dimensional-finite element dynamic analysis to validate the backcalculated modulus values.